The Messiah would be a witness.
OT Prophecy NT Fulfillment
Isaiah 55:4
Behold, I have given him for a witness to the people, a leader and commander to the people.
John 3:10–12
[10] Jesus answered and said unto him, Art thou a master of Israel, and knowest not these things?
[11] Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness.
[12] If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?

John 18:37
Pilate therefore said unto him, Art thou a king then? Jesus answered, Thou sayest that I am a king. To this end was I born, and for this cause came I into the world, that I should bear witness unto the truth. Every one that is of the truth heareth my voice.
Tanakh – Neviim – Isaiah 55:4
Behold, I have given him for a witness to the peoples, a prince and commander to the peoples.
Hebrew OT – Isaiah 55:4
[55:4] הֵן עֵד לְאֻמִּים נְתַתִּיו
נָגִיד וּמְצַוֶּה לְאֻמִּים